环境生态学Chapter7.ppt

The smallest population size needed to stay above the extinction vortex is often called the minimum viable population (MVP)
7.2.4 Reasons for Decline of Biodiversi Physical Alteration of Habitats The Population Factor Exotic Species Overuse
The value owenku.baidu.com natural species
?Sources for agriculture, forestry, aquaculture, and animal husbandry
?Sources for medicines, pharmaceuticals ?Recreational, aesthetic, and scientific
About 1.75 million species of
plants, animals, and microbes have been examined, named, and classified, but scientists estimate that
between 4 million and 112 million additional species have not
7.2.5 Convention on Biological Diversity (1992 in Rio de Janeiro)
?Adopt specific national biodiversity action plans and strategies ?Establish a system of protected areas and ecosystems within the country ?Establish policies that provide incentives to promote sustainable use of biological resources
3. Overhunting
Big-game hunting
4. Secondary extinctions
Loss of food species
Two basic causes for this extinction vortex
?One is that small populations may have breeding problems. ?The second cause is that small populations are much more easily wiped out by random environmental fluctuations
yet been systematically explored .
7.1.2 Two Kinds of Value
?instrumental value: its existence or use benefits some other entity ?intrinsic value: it has value for its own sake
Ecological extinction:
a species has become so rare that it has essentially no role or impact on its ecosystem
Table 7.3 Four ways that humans cause population decline and species extinction
Change physical environment: Examples
1.Habitat disruption
Drain swamp, toxic pollution
Change biological environment:
2.Introduce new species
New predator
Figure 7.1 Preserving 50% of total habitat area often leaves about 90% of the original species remaining alive
7.2.3 Extinction Species extinction:
a species has died out in a local area
Chapter 7
Conserving Biological Resources
Chapter 7Conserving Biological Resources
7.1 Value of Wild Species 7.2 Biodiversity
7.1 Value of Wild Species
7.1.1 Biological Wealth
the number of species that occur in an area
7.2.2 The species-area curve:
The number of species is counted in a gradually enlarged area of sampling, the result is a curve. The number of species rises rapidly at first, but it slows as the area of sampling increases because the same species are encountered again and again.
value ?Intrinsic value
7.2 Biodiversity
7.2.1 Concept
Biodiversity: the variety and variability among
living organisms and the ecological complexes in which they occur Species diversity: